Clinical records of the first 45 consecutive patients (66 lesions) in whom the Probe TM a balloon on the wire, was used for percutaneous transluminal coronary angioplasty have been reviewed. The aim of this analysis was to establish the efficacy and safety of this device. Majority of the lesions taken up were considered severe and difficult to cross. The probe was the 1st catheter used in 51 lesions (77%) and in 15 lesions (23%) it was used after other balloon catheters. In 88% (58/66) of lesions treated the Probe reduced the stenosis to less than 50% of the luminal diameter. Of the 45 patients treated 39 (87%) had a successful result. Of the 19 patients with multiple lesions 74% (14/19) had complete revascularisation and in 16% (3/29) had the most significant vessel dilated. Two patients (3%) required urgent coronary artery bypass surgery for acute occlusions. There was no hospital death. Of 50 probe devices used 5 (10%) malfunctioned: the balloon ruptured (at 5 Bars pressure) in 2 instances, balloon twisted causing "Volvulous" in 1 and balloon failed to deflate in 2 cases. The probe has significant advantages over other balloon systems for treating severe coronary lesions because of its low profile. It is however a delicate catheter system and prone to malfunction if not handled with care. Our results show that it is an excellent system for opening difficult and tight coronary lesions.